68HC11 Keypad interfacing

HI all,

I would like to build a hardware - 4X4 matrix keypad with use of IC MM74C922 base on Motorolla 68HC11 microcotroller, but I have no idea about the circuit design and the program, i wish everyone in this forum whose had experiance in this can help me and give any resources ...Thanks

In what language ?

Hai 3v0 thanks your speed reply...the project in assembly languang...asm

The 68HC11 is much more popular with schools the with hobby types. So this is a school project. If so you need to do your own work.

If you need to see a similar circuit design check out Nigel's


This is specific to the PIC processor but the same idea. You still need to write your own code. Which is the point right.

I have not written any HC11 code in about 10 years but I do not recall that it is esp difficult. Study the addressing modes and then keep your instruction referance card handy while you write your code.

This soft of stuff is actualy a lot of fun.
Good luck.

hi,
Download the 74C922 datasheet from www.datasheetarchive.com

It shows examples on how to connect a 4*4 or 4*5 keypad.

I have used the 74C922 in early projects, but they are not cheap, it would be more cost effective if you used the MCU to scan the pad.

thanks for 3v0 reply and i now have an Idea about it, this is the diagram of 68HC11 organisation after i hv got the idea from 3v0, i wish to do this following jobs if i apply the Port C (Bi-directional I/O) with use of the IC MM74C922N which the diagram of bottom, do it make sense?

Thanks ericgicbbs ur reply I hv download the above datasheets so may i know that do it possible if i connect the Port C (PC0 - PC3) to the IC MM74C922?

You can do whatever you can get to work.

If this is a learning exercise then I would scan the keypad with the processor. if it is a project where you need to conserve you ports for other hardware I would use the MM74C922N or some other decoder as suggeted by Chris.